The present invention relates to mattresses for beds. In particular, the invention relates to liquid-filled pads that substitute for conventional waterbed mattresses.
A unique attribute of a waterbed mattress is the floating sensation experienced by a user reclining on the mattress. This comfortable floating feeling, and the way in which the surface yields and conforms to the user's body, have contributed greatly to the commercial success enjoyed by waterbed mattresses. There are, however, certain disadvantages with ordinary waterbed mattresses that have limited their use and enjoyment.
One such disadvantage, occurring because of the compliance of the waterbed, is the possibility of excessive flexure of the user's spinal column into the waterbed mattress as the person lies on the mattress. Another disadvantage is the wearisome duration of wave motion of the water, that begins upon rapid movement by the reclining occupant and may continue for an extended time afterward.
A further disadvantage of existing waterbed mattresses is their inability to support concentrated pressure, resulting in a tendency to be depressed in the places where a person pushes upon the mattress to rise away from it. This can be particularly troublesome to persons who are restricted in the movement of their limbs.
Other disadvantages result from the large quantity of water utilized in a waterbed mattress. For example, the heavy weight of the filled mattress may overstress the structure of older buildings and makes transport of a filled waterbed mattress impractical even for short distances within a room. Additionally, the large body of contained water must be kept heated on a continual basis to avoid uncomfortable chilliness as the water absorbs heat from the user's body. Furthermore, there is an ever present danger of water leakage and consequent damage.
To address these problems, one approach used has been to use a waterbed mattress containing less water. It has been found, however, that a reduction in waterbed mattress height below four inches causes an undesirable "bottoming out" effect. The volume of water displaced when the user suddenly shifts position or sits up may be great enough that a portion of the occupant's body collides with the board or other rigid material used to support the underside of the waterbed mattress.
As disclosed by Rodinsky, U.S. Pat. No. 3,958,286, a pad for use atop a conventional mattress to extinguish fires and to provide desired support characteristics comprises a bladder having opposite upper and lower sheets interconnected with each other to define a number of individual, but internally interconnected, water compartments. Such pads, however, are not intended for nor apparently capable of providing the floating sensation that provides a waterbed with its unique character and advantages.
What is desired, then, is an improved bedding structure that provides the sensation of floating provided by a waterbed mattress, in conjunction with the firmness and the handling convenience of an innerspring mattress, while avoiding the disadvantages of previously available waterbed mattresses.